[CLN-list] I applied the patch

[Richard B. Kreckel]

Hi!

On 03/12/2012 05:53 PM, Alessandro PROFETI wrote:
> I wasn't very fast in downloading cln source code and applying the patch.
> Without the patch, the number in the last incomplete (no \n) line wasn't
> read by cin >> x.
> Now the behavior of operator>> is the same, the last number is read and
> printed in both
> cases; the next cin>>x results in an exception.
> This behavior is EXACTLY what I observe when x is a double, if I compile
> the file profeti.cc with the switch -DEXCEP.

Great. So that is fixed now. I've committed it.

> Is there a way for asking cln to behave the same way as c++ when
> extracting a cl_R,
> so that the code
> sum = 0;
> while (cin >> x)
> sum = sum + x;
> would compute the sum of the data, with x double or x in cl_R?
> This way of coding is much simpler then
> for (;;)
> {
> try {
> cin >> x;
> } catch ( ... ) {
> break;
> }
> sum = sum + x;
> }

Good point. I agree that, ideally, CLN would behave the same as standard 
C++ when reading numbers from streams.

Another issue is reading from an input stream that provides "123ABC". It 
seems like standard C++ reads 123 and stops there while CLN reads more 
and later discovers that ABC doesn't match the format.

> I tried to peep in cln source code and in the code for libstdc++, but
> couldn't figure out
> if there is some place in cln code when one can take in account the
> value of cin.exceptions()
> and react to error throwing an exception when the corresponding bit is set
> or returning a null reference (the default for cin >> x when x is
> double) when the bit is clear.

I think rather than resetting exceptions after the fact, the functions 
implemented in cl_*_read_stream.cc should be written to be more specific 
to the number format. They could then read only what is required.

I'll see if I can provide a patch.

Bye!
   -richy.

PS: I'm taking this thread to the mailing list.
-- 
Richard B. Kreckel
<http://www.ginac.de/~kreckel/>